This application claims the priority of German patent document 197 15 324,0, filed Apr. 12, 1997, the disclosure of which is expressly incorporated by reference herein
The present invention relates to a heat exchanger for liquid heat exchange media, especially for different fluids in separate circuits, primarily in internal combustion engines. More particularly, the invention relates to a heat exchanger which is supplied at its inlet with flows of a first liquid at different temperatures for alternate heating or cooling of the second liquid under valve control. A valve device located at the inlet is controlled as a function of an outlet temperature of one of the liquids.
A system of the type generally described above in a heat exchanger for an internal combustion engine is known, for example, from U.S. Pat. No. 2,670,933. In this known system, during warm-up of the internal combustion engine, the entire internal coolant flow is conducted through the water/lubricating oil/heat exchanger. When the internal combustion engine is subjected to a high load, an external cooling circuit is connected by a thermostatic valve, with all of the coolant being cooled down being fed back through the water/lubricating oil/heat exchanger of the engine. In an intermediate temperature range, the internal cooling circuit and the external cooling circuit of the engine are coupled together through an additional valve. This valve is designed as a three-way valve, and, depending on the temperature of the lubricating oil flowing out of the water/lubricating oil/heat exchanger, is controlled to produce a flow into the water/lubricating oil/heat exchanger that is a mixture of cold and hot coolant components.
To detect the lubricating oil temperature, an electrical temperature sensor can be used to produce signals which serve to control a positioning motor that is in a driving connection with the three-way valve. In another embodiment, the lubricating oil can be fed to a thermostatic device that is in a driving connection with the three-way valve. There is a significant risk that, in the event of damage to such an arrangement, each of the liquids can cross over into the other circuit of the engine and cause the engine to fail. Both systems are also costly to construct.
This disadvantage is overcome by a valve device located at the inlet of a water/oil heat exchanger as proposed in German patent document P 196 37 817. This device is composed of a hot inlet that is connected with the internal coolant circuit in a bypass flow and with a cold inlet that is connected with an air/water heat exchanger In internal combustion engines with a low heat impact during a warm-up phase, in order to enable the heating and air-conditioning system to begin operating quickly, the hot inlet is controlled by a thermostatic throttle valve and the cold inlet is controlled by a separate thermostatic valve. In internal combustion engines with a high heat impact during warm-up, instead of the two separately acting thermostatic valves, a single thermostatic valve in the valve device upstream from the water/oil heat exchanger can control the two intake lines. In order to reliably control the temperatures of lubricating and/or transmission oil over the entire operating range of the engine with this single thermostat, the operating opening temperature and the regulating temperature of this thermostat must be switched to cool operation. The operating opening temperature thus determined for the single thermostat, however, is disadvantageously low for warming up one or more oils using the water/oil heat exchanger. Consequently, during warm-up, the engine receives, from the water/oil heat exchanger, relatively cold coolant in the internal cooling circuit that is operable during the warm-up phase. This results in a disadvantage, since engine warm-up is delayed.
A goal of the intention is to design a coolant control for a heat exchanger such that, during the warm-up phase, the temperature of the coolant that flows out can be favorably adjusted to the temperatures of devices connected further downstream in the cooling circuit.
This and other goals have been achieved according to the present invention by providing a heat exchanger for liquid heat exchanger media in an internal combustion engine which has at least two different liquids in separate circuits. The heat exchanger is exposed on an inlet side to a plurality of flows of a first of the liquids. These flows are at different temperatures for alternate heating or cooling of a second of the liquids under valve control. A valve device located on the inlet side is controlled as a function of a temperature of one of the liquids on the outlet side. A temperature sensor is located in an outlet of the heat exchanger for the first liquid, serving for heating and cooling, for control and/or regulation of separate valves located in a hot inlet and a cold inlet for the first liquid in the valve device.
This and other goals have also been achieved according to the present invention by providing a cooling system for a motor vehicle, including a coolant cooler, i.e., a radiator, having an inlet communicating with an internal combustion engine via a coolant return line. A valve device has a hot inlet, communicating with the coolant return line, and a cold inlet communicating with an outlet of the coolant cooler. A coolant/oil heat exchanger has a coolant inlet communicating with an outlet of the valve device. A coolant outlet communicates with the internal combustion engine via an engine coolant supply line. A temperature sensor disposed in the engine coolant supply line controls the valve device to regulate a relative proportion of incoming coolant flow into the valve device from the hot inlet and from the cold inlet,
This and other goals have additionally been achieved according to the present invention by providing a cooling system for a motor vehicle, including a valve device having a hot inlet communicating with a coolant return line from an is internal combustion engine, and a cold inlet communicating with a coolant cooler, i.e., a radiator. A coolant/oil heat exchanger has a coolant inlet communicating with an outlet of the valve device. A coolant outlet communicates with an engine coolant supply line. A temperature sensor disposed in the engine coolant supply line controls the valve device to regulate a relative proportion of incoming coolant flow into the valve device from the hot inlet and from the cold inlet.
This and other goals have further been achieved according to the present invention by providing a method of controlling a cooling system for a motor vehicle including a coolant cooler, i.e., a radiator, having an inlet communicating with an internal combustion engine via a coolant return line, a valve device having a hot inlet communicating with the coolant return line and a cold inlet communicating with an outlet of the coolant cooler, and a coolant/oil heat exchanger having a coolant inlet communicating with an outlet of the valve device and a coolant outlet communicating with the internal combustion engine via an engine coolant supply line. The method includes the acts of arranging a temperature sensor in the engine coolant supply line, and controlling the valve device with the temperature sensor in order to regulate a relative proportion of incoming coolant flow into the valve device from the hot inlet and from the cold inlet.
According to the invention, a temperature sensor is provided in the outlet from the heat exchanger for the first liquid that serves for heating and cooling. The temperature sensor is provided for the control and regulation of separate valves located in a hot inlet and in a cold inlet for the first liquid in the valve device.
In the system according to the invention composed of a temperature sensor in the outlet of the heat exchanger, the temperature sensor is advantageously impacted by a coolant that has been optimally mixed, resulting in much smaller temperature fluctuations. In addition, the operating opening point can advantageously be set higher by comparison with heat exchanger input regulation. This has the advantage that the coolant in the outlet of the water/oil heat exchanger is at a higher temperature, so that the temperature of the coolant flowing out of the heat exchanger during the warm-up phase advantageously can be raised to the temperature of the coolant circulating in the internal cooling circuit. Engine warm-up time is thus significantly reduced.
In certain preferred embodiments of the invention, a wax-filled expansion element with a rod-type piston is provided as the temperature sensor, with the piston having two valve plates located at a distance from the expansion element such that with each maximum stroke of the piston, one valve plate is in the open position and the other valve plate is in the closed position. As a result, a simple valve device of advantageous design is produced. This device, in certain embodiments, is preferably made in the form of a separate part with an outlet located between the valves, through which the valve device can be tightly connected with the inlet to the heat exchanger. A piston, that may be formed by coupling two sections, links the valve device with the expansion element located in the heat exchanger outlet. This design allows simple assembly and avoids problems with the operation of the valves.
The heat exchanger according to the invention is preferably used for alternate heating and cooling of an oil for a drive assembly by means of the coolant in an internal combustion engine equipped with a coolant thermostat. The hot inlet of the valve device is connected with a coolant bypass on the engine, and the cold inlet of the valve device is connected with a low-temperature cooler located in the coolant circuit of the engine. In this design, when an oil is cooled by means of the water/oil heat exchanger, especially intensive cooling of the oil or oils is achieved.
In addition, the invention is preferably used for heating and cooling the transmission oil of the drive assembly. In addition, with a temperature sensor located for example in the transmission oil sump of the engine, the signals from this sensor can be used to control an electrical heating element located in the wax of the expansion element. The system, therefore, is configured to quickly move the expansion element, which is set for a higher operating opening temperature as well as a higher regulating temperature, into the open position as a function of the oil temperature reached in the transmission sump. With this system, the temperature of the coolant that flows out in the warm-up phase of the water/oil heat exchanger advantageously has nearly the same temperature as the coolant circulating in the bypass.
In another embodiment of the invention, the valves of the valve device are connected in a driving relationship either individually or jointly with a positioning motor. The valve or valves are controlled by amplified signals from an electrical/electronic temperature sensor.